The carbon in fossil fuels used to be in the atmosphere, but it's been sequestered for millions of years. Buring oil re-releases the carbon that had been sequestered so long ago. Think of that carbon as "old" carbon.

All animals living today, including humans, eat food that has sequestered carbon in it. But that carbon was absorbed from the atmosphere just a few months ago; it's "new" carbon. We eat plants and animal, metabolize the carbon, and re-release it to the atmosphere - it's considered "carbon neutral."

Activities you do that release "old" carbon are considered to increase the size of your "carbon footprint," but activities that release "new" carbon do not.

This is a vastly simplified explaination, but I think it explains why human breath doesn't contribute to greenhouse gasses.

With regard to reforestation: it depends where on the planet you live. In North America, reforestation is normal practice. But in many countries, it isn't.

And the carbon released by fossil fuels is not only from a long time ago, it also (and perhaps more importantly) took a long time to trap. In burning coal to generate electricity, we release in a single day an amount of carbon that took hundreds or thousands of years to trap. And gasoline is even worse.

Obviously, this is not a sustainable process. So, we might think to ourselves, "well, the problem will fix itself, then; eventually the available carbon will run out, because we can't keep releasing it at a rate greater than it is trapped." However, this will not happen untill we have burned up all the fossil fuels on the planet, releasing hundreds of millions of years worth of carbon in just a couple of centuries.

matthyaouw: that source was pretty interesting - it shows that transport gas usage is extremely small compared to what industries use.

Ok, so I understand now that Fossil Fuels and Deforestation is still the main issue.
Now, all these "save the world" commercials and advertisements talk about making the "little" change where we need to switch of an unused lamp or just a cell phone charger with no phone on it...
Are these people just "over" exaggerating the global warming concept?? I don't imagine that the few watts of power a lamp consumes (compared to a continually running refrigerator) and a cell phone charger with NO load can help by just turning it off...

Power plants are generating MW to GW of electricity which I'm sure primarily goes to industries, so am I wrong too disbelieve people who are taking the global warming issue far too 'out of hand'?

There is also the concern whether you switch your vehicle to diesel or lpg - which is the better of the two?